<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>哈哈,我又变帅了</title>
    <style>
        * {
            margin: 0px;
            padding: 0px;
        }

        body {
            background: url("../images/1.jpg");
        }

        #mask {
            background-color: rgba(255, 255, 255, 0.3);
            height: 200px;
            text-align: center;
        }

        #mask img {
            width: 200px;
            margin-top: 35px;
            cursor: pointer;
        }

    </style>

</head>
<body id="bd">
<div id="mask">
    <img src="../images/1.jpg" alt="">
    <img src="../images/2.jpg" alt="">
    <img src="../images/3.jpg" alt="">
</div>
<script src="common.js"></script>
<script>
    var imgObj = my$("mask").children;
    for (var i = 0; i < imgObj.length; i++) {
        imgObj[i].onclick = function () {
            document.body.style.backgroundImage = "url(" + this.src + ")";
        };
    }

</script>

</body>
</html>